Shortcuts always cost more. Like the Bulldog to the T54E1 for instance. But they also costs more since tier 8 LT's don't have to spend 50K XP on a gun, or 25K on a turret or 20K on engine and tracks. Thus usually the XP needed for the next one is higher vs most tier 9 unlocks, even if it's not a shortcut. As the module unlocks costs way less. Another example would be the Tier X German light. It costs over 100K more to unlock vs even the E100. But again.. the tier 9 RU only have tracks and engine for most. Thus 50K xp in modules. Not 160K like the E75 etc.